A few scientific packages are compiled with icc (intel compiler) instead of gcc, among them python 2.7 and 3.2. However, this is also the case for the laptop, where everything works. I just followed the guide for icc on the Gentoo Wiki.

I even reinstalled the reference packages for blas, cblas and lapack, set the corresponding eselect options accordingly and recompiled numpy and its dependencies to no avail.

I'm completely clueless. Any idea is welcome. Since I have a working system (the laptop) it will be easy for me to check whenever you tell me to.